Northern Grasshopper Mouse
Order Rodentia : Family Muridae : Onychomys leucogaster (Wied)

Description. A stout-bodied, short-tailed mouse similar to O. arenicola but larger, heavier, and shorter-tailed; upperparts drab brown; the nose, sides, cheeks, and underparts white; tuft at anterior base of ear white and conspicuous; tail usually less than 30% of total length and usually from 1¹/2 to two times as long as hind foot. External measurements average: total length, 164 mm; tail, 42 mm; hind foot, 22 mm. Weight, 27-46 g, occasionally as much as 52 g.

Distribution in Texas. Throughout most of western Texas (except the central part of the Trans-Pecos) and the Rio Grande Plains of South Texas.

Habits. These "predatory" mice occur chiefly in association with sandy or powdery soils in grasslands or open brushlands, but they are never very common as compared with other small mammals.

They are wanderers and do not live long in one place. They are reputed to usurp the burrows of other small mammals rather than take the time to construct their own. This is in keeping with their pugnacious disposition. Vernon Bailey attributes to them many of the habits of the weasel and compares one of their calls with the howl of a wolf which "is made with raised nose and open mouth in perfect wolf form." Because of their short legs and chunky body they are not fleet-footed, but they are expert at dodging, twisting, and turning and in close quarters can easily capture and overpower other mice their own size or even larger.

As the name implies, one of their chief food items in season is grasshoppers. In addition, numerous other kinds of insects, scorpions, small mice, and a variety of plants contribute to their diet. Captives are especially fond of raw liver and newborn mice. Vernon Bailey and Charles Sperry report that animal matter makes up nearly 89% of their natural food; plant material comprises only 11%.

The breeding season extends at least from May to October, as judged from pregnancy records. The capture of half-grown young in the dark juvenile pelage from February to September indicates that some breeding occurs throughout much of the year. The bulk of the young are born in May and June, however. The litter varies from two to six; average about four.

The gestation period varies from 32 to 47 days, with the longer periods in lactating females. At birth the young are pink and hairless (except for the prominent vibrissae), and weigh about 2 g each. The eyes and ears are closed, and the tail is characteristically short and thick. Within 3 days the ears unfold, but the eyes remain closed until the 19th or 20th day, at which time the young mice are almost weaned. They are probably evicted from the nest shortly after. Sexual maturity is reached in about 3 months when the mice are still in the soft, gray juvenile pelage.

Because of their fondness for insects and small mice their economic status is either neutral or beneficial.

Photo credit: R.D. Porter.